Before you even get to a national park, know how to use your camera. Learn your camera's various features. Practice focusing and using the zoom features. Wildlife will not pose or wait for you to figure your camera out. So be sure you know what to do that exact moment a picture perfect scene arises. Wildlife can wander by at any time and just about anywhere in a national park. Be prepared. Always have your camera with you and turned on, so make sure its fully charged.
If your camera has a continuous shooting feature, use it. This way you can capture a sequence of images as an animal quickly passes by and choose the best photograph later. Try to fill the frame of your camera. Use the zoom of your digital camera or a telephoto lens for a 35mm camera to get a close photograph. If that's impossible, don't worry. It's still better to get a small photo of an interesting animal than nothing at all. Try to get a natural background behind the animal you are photographing. Just by shifting the angle of a photograph you can get trees, mountains or sand in a photograph instead of people, signs, picnic tables and cars. This makes a more interesting and natural photograph.

A-C Photo by Gary Bodiford
Buffalo in Wichita Mountains
Some national parks are actually marine sanctuaries underwater. You can capture the beauty under the sea with an inexpensive disposable underwater camera. Make sure the disposable camera you buy is rated to go underwater, not just waterproof for the surface. Don't always think big animals. The small rodents, birds, and insects in any environment make just as interesting photographs as the larger deer, elk, and alligators. Take lots and lots of photos. If you happen to be in a location when there's something exciting to photograph, don't settle for one shot. Taking multiple exposures allows you to choose the best photograph later.
Once you return from the national park you can use photo-editing equipment to enhance your wildlife photographs. Most camera shops have kiosks where you can enlarge and crop your raw images before printing. You can also use photo-editing software on your computer such as Photoshop or Photo Essentials to enhance your digital photos at home.

A-C Photo by Stuart Marks
Wildlife in Cades Cove. Great Smoky Mountains
Tips/Warnings:
When you first arrive at any national park, visit the Visitors' Center to get a better understanding of where to find wildlife in the park and safety instructions. Wildlife should not be approached or chased. Follow all rules and guidelines posted in the national park about wildlife. Wildlife should not be fed. Yes, sometimes you can get a better photo if an animal is being fed, but it's not worth it. First be stewards of the environment and do not risk the health of an animal just to get a better photograph. People have been hurt approaching wildlife for a better photograph. One never knows when an animal will turn. Always keep at a safe distance.
Source: eHow.com
By Carla Lucas